This invention relates to devices for spinal etc. fixation, of which one known type (GB-PS 2 151 928A) consists of stainless steel or titanium round rod of 3/16" or 4.7625 mm diameter formed into a rigid rectangle with its shorter sides bent (e.g. into or including a curve) in the same direction from the plane of the longer sides which are adapted to fit substantially parallel to the length of two or more bones of the spine with the shorter sides accommodated between respective pairs of adjacent spinous processes, the rectangle being fixed in place to immobilise the bones with respect to each other by means of wires or other strands around or looped through the rectangle and passing through holes in the bones.
The bending (and/or curving) of the shorter sides enables the longer sides of the "roofed" rectangle to fit more closely upon the transverse processes of the bones of the spine than the previously "flat" rectangle and therefore it appears less bulky. This reduces dead spaces between the device and the spine, thus effectively reducing the risk of haematoma and infection, whilst being biomechanically more efficient. Correct fixing of the "roofed" rectangle is more consistently obtained because wires or other strands looped through the rectangle round the shorter sides are automatically guided down the "slopes" of the shorter sides to rest at the corners formed with the longer sides. Furthermore, because the "roofed" rectangle makes a better fit and affords greater inherent torsional rigidity than a flat rectangle, it gives much greater control of rotation of the immobilised bones with respect to the remainder of the spine.
The "roofed" rectangle if the first implanted device to give the spine effective torsional rigidity, therefore allowing immediate mobilisation following surgery, without the need of any external cast or brace.
The shorter sides generally lie in parallel planes, perpendicular to the plane of the longer sides, and each shorter side has two straight portions at an angle to each other of between 90l .degree. and 110.degree., with a small radius curve between them and small radius curves at the corners formed with the longer sides.
In addition to providing "roofed" rectangles of different lengths and/or widths, the shorter sides may have different "roof" angles, to suit different sizes of bones and/or bone combinations.
However, "roofed" rectangles as described above, while proving to be a vast improvement compared with previously known devices, particularly in view of their simplicity and secureness, have one disadvantage in that to accommodate the two shorter sides closely between the spinous processes of respectively pairs of adjacent bones of the spine it is necessary to sever the two ligaments between those respective pairs of spinous processes.
One object of the invention is, therefore, to provide an improved device for spinal fixation which additionally provides fixation of a skull to adjacent bones of the spine to assist in holding up the head.